This invention relates generally to a mechanism for coating an airborne stream of small granular items, such as seeds, with a substance in liquid or liquid-like form, including a powdered solid, and, more particularly, relates to the use of a on-board seed coating apparatus for air seeders and the like. A particular example of the use of the invention lies in agricultural implements such as seed drills in which the implement carries, or operates with, a reservoir of seeds, and is effective to transfer the seeds into the ground over a substantial area while moving across the field. The invention may be utilized for coating seeds with agriculturally-effective substances, such as inoculants, fungicides, etc.
Seeding implements are well known. Implements such as air seeders convey the seeds from the reservoir to the seed deposition outlets of the implement by means of a flow of air through conduits. The air flow is derived from a fan or air compressor, which typically is mounted on the implement and powered by the prime mover, normally a tractor.
Typical known seed coating processes for coating seeds have generally been carried out on an in-factory basis. That is to say, machinery is provided in which, for example, seeds are mixed with a coating material in a fluidized bed arrangement. Because the coating process is carried out in-factory, it is a relatively easy matter to ensure good quality control, especially as regards the thickness of the coating, and as regards the evenness of the thickness, over the seed, and seed to seed. When the coating is factory-applied, inevitably a long time must elapse between the application of the coating and the insertion of the seed into the ground.
Another known method of coating seed is the mixing of batches of seed with treatment fluid on the farm prior to placing the seed in the air cart tank. This system is inefficient and requires the operator/farmer to handle the coated seed in some manner. Seed coated in this manner must be used within a limited time frame of when it is coated, and thus coated-seed not planted within a given time frame becomes wasted. This translates to losses due to the costs of wasted seed and wasted treatment fluids. This method also requires cleanup of the air cart tanks and loading equipment after treated seed is handled.
An important requirement is that the seed be coated evenly, not only over the surface of each seed particle, but also from seed to seed. Accordingly, an important goal would be the application of the coating to the seeds without compromising evenness and controllability of the coating, even though the coating operation is done actually on the air seeder, and takes place even as the operation of seeding is being carried out.